# -*- coding: utf-8 -*-
# @Time    : 2021/4/15 0015 16:58
# @Author  : 蒋才果
# @Email   : 1476235300@qq.com
# @File    : 输入输出正整数.py
# @Software: PyCharm
while 1:
    num = input("输入一个正整数：")
    if num.isdigit():
        print(num)
    else:
        continue